Amplifying horn



NOV. 24, 1931. J AUERHAAN v 1,832,851.

AMPLIFYING HORN Filed Aug. 23. 1929 2'Sheets-Shee1 1 Nov. 24, 1931. J. J. AUERHAAN AMPLIFYING HORN Filed Aug. 23, 1929 2 Sheets-Sheet 2 Patented Nov. 24, 1931 UNITED STATES JOSEPH J. AUEBHAAN, OF BROOKLYN, NEW YORK AMPLIFYING HORN Application filed August 23, 1929. Serial No. 387,930.

My invention relates to horns for amplifying sounds reproduced mechanically or electrically as by the well known phonograph or radio methods, or for amplifying sounds produced in any other manner, and more particularly my invention relates to the large so called exponential horns employed for amplifying such sounds in large or open spaces as in theatres, concert halls, or outw door places.

The object of my invention is to provide an improved method of producing such horns whereby successive layers of the material of which the horn is constructed may be 1.3 built up evenly to provide uniform density to the walls of the horn, minimum of vibration, strength and rigidity, and whereby all warping, buckling or bulging in the finished product may be obviated.

In carrying my invention into efiect I employ a mould or core upon which the horn is built up. For the large exponential horns of approximately nine, or ten or more feet in length, and which may be either straight or turned into a volute spiral, I prefer to employ a sectional mould or core made of a light metal, such as aluminum, in about eight sections; the large or bell-end section having a flange against which a corresponding flange is formed on the built-up born. The core sections are preferably hollow and keyed or otherwise detachably secured together on the inside so that they may be removed sectionally when the moulding operation is completed.

In building up the horn upon the core I may employ various materials such as paper, chip-board, cloth or other woven fabric, such material being employed alone or in combination. I prefer however to employ paper or chip-board of different thicknesses in alternating layers, the layers being composed preferably of 21 or 22 point chip-board alternating with 38 point chip-board, such thicknesses alternating up to the desired thickness for the walls of the horn and the thinner board preferably constituting the first or inside layer of the horn and the thicker board being preferably employed for the outside layer. When paper or chip-board is employed for the horn it is preferably prepared for use by first dipping or soaking sheets of suitable size in water and allowing the sheets to drain off. The wet sheets of one gauge are laid on the core in a single 5 layer while wet and in a pulp-like condition, the core having been previously smeared with a heavy Oll or grease. To produce a flat even surface and to work out all creases or wrinkles caused by bending the paper to the curves of the core, and to further pound the paper into a pulp-like condition, it is hammered or pounded by a sort of rolling action with a suitable mallet or pestle-like tool having a relatively large rounded working surface. The lirst layer of paper is then smeared over with a suitable paste and the second or heavier layer of wet pulp-like paper is applied in the same manner as the 7 iirst layer. 'l'his is contlnued until the desired thickness is obtained, and then the mass is baked, preferably for a period to obtain only partial drylng out of the paper, and then the mass is removed from the oven and 7; the core removed. The horn at this stage is allowed to airdry. This manner of building up the horn serves to bring the successive layers of paper into a dense mass almost like pulp owing to the heavy wet paper being 80 pounded, and the paste being thoroughly spread over and driven into the paper, and the slow heat and air drying, all result in producing a horn mass that will not split between paper layers, crack, bulge or Warp. The dried mass is rubbed smooth on the outer surface, the inner surface being smooth owing to the smooth hard core surface, and finally the horn is shellacked, painted, or

otherwise coated to prevent absorption of moisture, and to impart the desired finish.

My invention is illustrated in the accompanying drawings in which Figure 1 is a perspective view of a sectional mould or core for the large exponential type of horn, the larger or bell-end having a laterally projecting flange; Figure 2 an enlarged sectional. view showing the upper or lower bell flange of the core and the aPPlICtItIOD' of the first two layers of paper to the core; Figure 3 a cross section of a corner of the core showing the overlap of the paper at the four corners of the horn; Figure 1 a perspective view of a bell-frame which is built into the horn to reinforce the bell of the horn; Figure 5 an enlarged sectional view showing the upper or lower bell flange with the first two layersof paper wrapped around the belleframe; Figure 6 a view similar to Figure 5 but showing either of the side flanges of the bell-end of the horn and which view illustrates the difference in flare in the side walls as compared to the top and bottom walls illustrated by Figure 5; Figure 7 a cross section of a corner of the core and paper layers showing a further development of the overlap as started in Figure 3;'Figure 8 a perspective View of the paper horn as built-up on the core and iliustratmg the stage ,of production either before or after the core is removed; Figure 9 a perspective view of the horn after it is heat cured, air dried, rubbed clown, painted and shellacked, and with the supporting rack built thereon, but before the small or speaker-end is placed in position; Figure 10 a perspective view of the speaker-end of the horn; Figure 11 a partial perspective like Figure 9 but showing the speaker-end of the horn in position; Figure 12 a partial side elevation showing the retaining yoke for the speaker-end of the horn and a ferrule block mounted on the yoke; Figure 13 a horizontal section on line 13-13 of Figure 12 showing a plan of the yoke and ferrule block; Figure 14 an enlarged view showing a part of the speaker-end of the horn, part of the yoke, the ferrule block in cross section, the ferrule in the small end of the horn, and the speaker unit mounted on the ferrule; and Figure 15 a perspective View of the complete horn.

Referring to Figure l of the drawings, which illustrates the preferred form of core for a large horn having its small end curved back into volute spiral form, it will be noted that the core is made up of a number of sections, and that there may be as many sections as the size and shape of the horn to be produced thereon may dictate. In Figure l the core is shown as made of seven sections as indicated at 1, each section being of gradually increasing size, and a large or bell section 2 having a flange 3 about two or three inches in width, extending entirely around the boll-end of the core. The flare of the core at the bell-end is about the same at the top and bottom walls 4 and 5, but the side walls 6 have a greatly reduced flare as will be more readily seen by a comparison of Figures 5 and 6 which show enlarged sections of bottom wall 5, side wall 6, and bell-flange 3. As above stated the core is preferably made of metal and as light as possible, therefore, it is preferably made of aluminum, and I also prefer to make the core sections hollow. The core sections will be so formed that the joints between sections will be as close and as smooth as possible so that no breaks or ridges Will be formed on the interior surface of the built-up horn. These sections will be locked to each other in any suitable manner, but since the core, per se, forms no part of the present invention the details of the joints and locking means are not illustrated. It will be understood that while I have shown a core which is rectangular in cross section, 4

my method of building-up the horn is not limited to the production of that type of horn. The horn may be circular or oval or of any other form in cross section, and the mould or core, of course, will have a corresponding shape.

The paper or chip-board sheets may be of any desired or standard stock size, or they may be specially cut to match the taper of the core sides 1, 5 and 6. In laying the paper on the core, or one layer uponthe other, all crosswise joints between sheets extending lengthwise of the horn, if the sheets are not of the full length of the horn, will preferably be butt-jointed. I prefer, however, that the layers of paper for each side of the horn, when the horn is rectangular in cross-section, shall be the full length of the horn, to avoid crosswise joints, and in the case of the first two layers 7 and 8, as shown in Figure 2, the

strips of paper will be longer than the horncore and extend beyond the bell-flange for the purpose hereinafter explained.

One of the important steps in my method of building up the horn on the core, is to soak the paper or chip-board sheets in water until thoroughly saturated throughout, allowing the water to drain off until the sheets are in a condition to permit handling, and then applying the wet sheets to the horn core.

The first step in the building of the horn upon the core is to coat the outer surface of the core with a thick fluid or slush, preferably oil or grease. The next step is the application of the first layer of paper, chipboard or other fabric 7 which is laid the full length of the core on the oiled or greased surface with a suitable length overhangin the flange 3 as shown in Figure 2. For the first layer I preferably employ chip-board of the thinner stock above mentioned, and after one sheet is spread out over one side of the core, as for instance, on side 6 of the core, see Figure 3, and its longitudinal edges bent over the corner of the core as shown in Figure 3, it is hammered or pounded flat and even as with a mallet or hat or large round-headed pestle like tool which will be manipulated with a'rollin action, to cause the pa er to conform to the shape of the core an even out all creases or wrinkles. When this sheet is thoroughly evened out, a sheet of the same thickness is laid on the side 4 of the core, and similarly hammered down with its longitudinal edge overlapping the overlap from the side 6, and the two overlapping edges are hammered down as close and even as possible as shown in Figure 3. The same operation is repeated on the other two sides of the core.

and similar overlaps made at each corner, and with the same overhang of the sheets 7 at'the flan e 3 as on the side first laid and as shown in ligure 2, and so that all four sides will have the same amount of overhang. The next step is to coat the first layer of wet pa ervthus laid on the core with a layer of thic pas-e, by hand or otherwise, and upon this coating of paste is laid the second layer of paper 8, also with an overhang at the flange 3, as shown in Figure 2, and this layer is applied in single sheets on one side of the core at a time, hammered down, and'the corners overlapped as shown in Figure 3, in exactly the same manner as wi;h the first layer of paper 7. This layer of paper, however, is of the thicker stock as indicated by the different thicknesses shown in Figures 2 and 3. The next step is to place the re-enforcing frame 9, shown in Figure 4, in position over the first two layers of paper 7 and 8 as indicated in dotted lines in Figure 2, the side of the frame next to sheet 8, or the sheet its-elf, being coated with paste. This frame is preferably made of wood, the four sides being joined in any suitable manner, and the corners being made square as shown, or rounded if desired, and the dimensions of the sides being approximately one by two inches. The frame when placed in position is hammered against the paper and flange 3, and then the other sides are coated with paste and the overlapping ends of the four sheets 8 are wrapped around the frame and hammered closely around all corners. The three exposed sides of the paper covered frame 9 are now given another coating of paste, and the four sheets 7 are similarly wrapped around the frame and hammered down. This condition of the building up of the horn is shown in Figures 5 and 6, before, however, the other sheets are added.

The layer of paper sheets 8 are now coated with paste and a third layer, which will be of the same thickness as the first layer, is applied with its edge abutting against the paste coated edge 10 of the paper covered frame9. These sheets will be applied in all other respects the same as the first layer, with the overlap at the corners of the core, and the of horn is of sheets applied and which layer will be of the heavier stoc the corners overlapped, and thewhole smoothed out by hammering as with the other layers, and the edges abut.- ting against the frame 9. This operation is now repeated with alternate layers of light and heavy paper until the desired thickness 0 tained as indicated by the sheets marked 11 in Figures 5, 6 and 7, and each succeeding layer overlapping at the corners as indicated approximately in Figure 7. I

have found in practice that by hammering the edges of sheets 11 close against the frame 9 that the pulp-like paper and paste make a close goint and that perfect adhesion is obtaine but if desired, the angle formed at the frame 9 and layers 11 may be filled by a fillet of paper as indicated by the dotted line 12 in Figures 5 and6, and which fillet when used will be hammered hard into the recess.

When the final layer of paper is applied, that layer bein of the heavier paper stock, the horn core with the built-up paper thereon is placed in a baking oven. The drying in the oven is discontinued while a slight amount of moisture still remains in the paper,

and the core is then removed by unlocking the sections and removing the large or hell section and successively removing each smaller section. The paper horn is thenset out for final air-drying. Owing to the manner of applying the wet paper and paste and the hammering of each successive layer in the building-up process, the paper layers assume a dense pulp-like mass, and then with the baking and final slow air-drying I find that there can be no separation between the layers of paper and that warping or bulging after drylng is entirely obviated.

After the horn is thoroughly dry, the out side surface is sand-papered to remove any high spots and to give a smooth finish to the surface. This is not necessary for the inside surface of the horn because due to the smooth surface of the core and the hammering down of the paper layers, that surface will come out sufliciently smooth. This condition of the horn is represented in Figure 8 of the drawings in which 13 indicates the hardened paper mass so intimately hammered together that the several layers of paper, which when applied were so wet that they were more like pulp, now appear as one thickness of paper re-enforced at the bell-end with a flange 14 and thus presenting a self-sustaining horn structure. The outside surface of the horn is now coated with a paint sizing and when dry is given a finishing coat of paint. The inside surface of the horn is then cleaned of grease in any suitable manner and a coat of shellac applied. I find in practice that wh at ever grease adheres to the inside surface of the horn is readily absorbed by shellac and that therefore a preliminary cleaning for removing the grease is not necessary. This coating of shel ac may be applied by di ping the entire horn into a shellac bath or t e interior may be coated and the grease -absorbed by flowing the shellac through the horn.

While the horn as this produced is selfsustaining, it is preferable to mount it on a. rack to support it in the position of Figure 8, or at any other desired angle, and for this purpose a rack is built about the horn as indicated in Figure 9. This rack consists of two bottom pieces 15 secured perpendicular to the bell-flange 14; two oblique bracing ieces 16 extending between the outer ends 0 the bot; tom pieces 15 and upper ends of side flanges 14; a bottom cross-piece 17 tying the bottom pieces 15 together; and a central cross-piece 18 secured to the oblique braces 16 and laid against the underside of the horn about midway its length. The cross-piece 18 is shorter than the bottom cross-tie 17 so that in securing it to the oblique braces 16 they will be drawn in against the sides of the horn. Fastened to the inner sides of the braces 16 and the middle cross-tie 18 are pieces of felt or other suitable material 19 to cushion the contact between those parts of the frame and horn.

The small or speaker-end 20 of the horn is shown in perspective in Figure 10. This small horn member is made up of thinner paper layers, about sixteen in number, but it is treated in the same manner as the large horn member and built up on a suitable core. The small end of this horn member 20 is preferably finished straight without flare or offset as shown at 21, while its larger end is built with a flange or collar 22 adapted to receive the small end 23 of the horn member 13, and the bore of horn member 20 will be such that the diameter at the seat of collar 22 will make a flush joint with the bore at end 23. The joint between the end 23 and collar 22 is made and sealed with glue and an iron filler. Horn member 20 and the curved part 24 of the large horn member form a volute spiral as shown in Figures 11 and 12.

A yoke is built around the spiral part of the horn for protecting the spiral and as a support for the speaker unit. This yoke consists of two long arm pieces 25 secured perpendicularly to the top side of the bell-flange 14 and placed against opposite sides of the spiral horn section as shown in Figures 12 and 13. Two cross-pieces 26 are laid across arms 25 and secured thereto so as to secure the throat of the horn. Pieces of felt lining 27 are provided on all four sides of the yoke where it is in contact with the horn to cushion the throat of the horn in the yoke. A ferrule block 28 is also secured across the top side of the yoke. This block has a hole drilled and is also recessed as shown at 29, Figure 14, to receive a flanged ferrule 30. The ferrule is glued to-the end of the horn and its flange is screwed to the ferrule block. The ferrule has a screw-threaded extension to receive the s eaker unit 31. A felt covered wedge 32 igure 15, is driven between the larger end of the horn member 20 and the bell part 13 of the horn body and same is secured in position by a screw or otherwise. This wedge serves to further secure the small end of the horn and at the same time cushion the contact between these parts of the horn.

While I have described the built-up layers of paper as starting with sheets of thin stock and the building-up proceeding alternately with thin and heavy stock, this practice may be varied, or sheets of uniform thickness may be employed, but I have found the arrangement as above described to be preferable. Nor do I limit myself herein to any prescribed thickness for the several layers of aper. It will also be understood that the lOIIl may be finished in one section without the use of the small horn section 20, but for practical reasons. especially when a spiral form is employed, I prefer the two section arrangement because it simplifies the building-up process and avoids difliculties which would otherwise be encountered in the core construction and withdrawal from the finished horn. It will also be understood that I do not limit myself to the precise arrangement of supporting rack and yoke shown and described. Furthermore, other modifications in details such as the form and material of the bell-frame 14, the manner of. finishing the exterior and interior surfaces of the horn, the form and mode of attaching the connection for the speaker unit, etc., may be made without departing from the spirit of my invention.

' I do not claim herein the invention involving the method of producing the amplifying horn as herein described since that invention is embodied in the divisional application filed by me September 16th, 1931, Serial No. 563,048.

What I claim is:

1. A sound amplifying horn consisting of built-up layers of moist, pasted paper formed into a dense mass.

2. A sound amplifying horn consisting of built-up layers of moist, pasted paper pounded into a. dense mass.

3. A sound amplifying horn consisting of built-up layers of moist, pasted paper formed into a dense mass, and a re-enforcing frame imbedded in the bell-end of the horn.

4. A sound amplifying horn consisting of built-up layers of moist, pasted paper pounded into a dense mass, a re-enforcing frame imbedded in the bell-end of the horn,

through it to receive the end 21 of the horn,

and a supporting rack surrounding said horn and secured to said frame; I v 5; A sound amplifying horn consistin of a body built into spiral form with bu1 t-up Y 5 layers o f moist, pasted paper formed into a dense mass, a re-enforcing frame imbedded in the bell-end of the horn, a supporting rac'k surrounding said horn and secured to said frame, and a yoke also secured to said frame 10 and embracing the spiral part of the, horn;

This specification signed; at New York city,

in the county and State of New York, the 7th day of August, 1929.

, 15 JOSEPH J. AU BHA 7 1 I. 

